Adjustable dielectric heating equipment



R. H. HAGOPIAN 2,629,812

Feb. 24, 1953 ADJUSTABLE DIELECTRIC HEATING EQUIPMENT Filed Sept. 20, 1947 34 ,e 32 A54 T I. Z 36 W 14 D Q L n m y a 4 5 o 1 0 z' 2. y Y 9 H w 40 24 ,za a4 40 42 4?0 18 14 312 30 P I 23 04 16 42 044 52 A 14 5? 44 42 o u i q w L'I t E o 1 g. a. lg /8 416 1 6 42% F O 36 34 30 332 1 I INVENTOR WITNESSES:

Richard H Hago bian mwz Patented Feb. 24, 1953 UNITED STATES PATENT OFFICE ADJUSTABLE DIELECTRIC HEATING EQUIPMENT Richard H. Hagopian, Halethorpe, Md., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application September 20, 1947, Serial No. 775,292

20 Claims. 1

tance, at the supply frequency, that is determined by the physical construction and set up of the heating-electrodes and the physical constants of the material therebetween. Such a capacitor ha a Q factor which is dependent upon the capacitance and the effective resistance of the material. Wide heating-electrodes can heat an elongated material of corresponding width; but if an elongated material of much narrower width is to be heated by the same heating-electrodes, the Q factor may rise to the point where power transfer from a high-frequency transmission line, or other power supply, to the heating-electrodes may be seriously impaired. The power transfer may become so low as to be insufiicient to heat the material properly, or the power transfer may become so inefficient that corrective measures are justified.

In systems in which a high-frequency transmission line feeds the high-frequency energy into the heating load comprising spaced heating-electrodes, it is desirable to have the transmission line feed its energy into a load impedance, looking from the transmission line, which approaches the surge or characteristic impedance of the transmission line. the width of progressively moving material to be heated may have a large and detrimental effect on this impedance matching. This detrimental eifect on the impedance matching can be partially or wholly counterbalanced in accordance with my invention, by a correspond-' ing change in the width of the heating-electrode. Such a change also keeps the Q factor more nearly constant.

For further providing a better impedance matching when the heating-electrode is changed.

in width, an embodiment of my invention in-- corporates a variable inductance across the spaced relatively insulated heating-electrodes. A network, consisting of the inductance in parallel with the capacitance between the heating- Changing width of the heating-electrode.

electrodes is thus formed. In one embodiment of my invention, to which I am not limited, the inductance is automatically increased or decreased by the same means which alters the This increase and decrease of inductance can be such that the network will remain substantially of the same effective impedance at the frequency of the power supply.

It is an object of my invention to provide a single dielectric heating means energized from a single source of high-frequency power, but

capable of satisfactorily and efliciently dielectrically heating materials, or work, of various sizes and girths.

It is a further object of my invention to provide a dielectric heating means comprising a heating-electrode of comparatively large area but adjustable in one direction, for example, in

width; the heating-electrode, however, presenting a continuous and smooth surface toward the material or work being dielectrically heated. A further object of my invention is to provide a dielectric heating means for heating traveling material, the heating means having an adjustable heating-electrode of the type described, which can be quickly and easily changed to accommodate the width of the material being heated.

A further object of my invention is to provide .a dielectric heating system of a type described, having an adjustable heating-electrode, with a variable inductance coil which is automatically varied whenever the heating-electrode is changed, for maintaining the electric relations of the network which includes the heating-electrodes.

Other objects, features and innovations of my invention will be discernible from the following description and generally schematic drawing of preferred embodiments, which are addressed to one skilled in the art who will readily understand .how various parts of the embodiments, teaching the principles of my invention, can be altered without departing from the spirit and limits of the invention. In the drawing:

Fig. 1 is a view, partly in side elevation and partly in section, of an embodiment of my invention in which material or work is carried through a dielectricheating means on a conveyor;

Fig. 2 is a vertical view, at a right angle to Fig. 1, partly in elevation and partly in section,

* of apparatus in accordance with Fig. 1;

Fig. 3 is a vertical sectional view substantially on the line III-III of Fig. 2;

Fig. 4 is an edgewise view of the adjustable heating-electrode of Figs. 1, 2 and 3;

Fig. 5 is a sectional view substantially on the line VV of Fig. 2; and

Fig. 6 is a fragmentary view corresponding to a portion of Fig. 1 but modified therefrom in several respects.

In Figs. 15 a dielectric heating means is shownv which embodies my invention. The dielectric heating means comprises an upper heating-electrode 2 spaced from and insulated from a lower heating-electrode 4. Preferably the. heatingelectrodes are of metal and have facing planar surfaces 0r faces of relatively large area or expanse to provide a work-space 6 therebetween. When the heating-electrodes are energized, as for example through high-frequency conductors 5, a; high-frequency field is established in the workspace 6; and a dielectric material, such as, for example, rubber mats, therein will be heated. An upper run 8 of an endless conveyor l0 passes longitudinally along the top of the lower heatingelectrode 4, and carries the work W throughthe work-space B for dielectric heating. 'I'heconveyor may be slowly'and continuously moved through the work-space Bor may be moved intermittently in steps.

In the embodiment being described, the" lower heating-electrode 4 is fixed in size and position, and is, preferably, grounded. The upperheatingelectrode 2 comprises a continuous flexible metal strip l4whi'ch has a fixed dimension, in this'case length, in the direction in which the upper run 8 travels. In a transverse direction, shown'in Figs, 2 and 4, the strip I 4 has a variable dimension, in this case width, so that it can bead- -justed to correspond to the width of whatever material is to be heat-treated or to the capacitance desired in the dielectric load consisting" of the heating-electrodes and the material therebetween. To this end I provide separate spaced bar members or shafts l6 and [8 at opposite sides of'the heating-electrode 2 and aboutwhich end portions of the metal strip Mare spirally wrapped. The shafts l6 and I8 are arranged at opposite lateral sides of the Work-space 6 so that the effective area of the upper heating-electrode 2, which bounds or terminates the high-frequency electric field across the work-space 6, constitutes substantially the fiat portion of the strip M, or that portion which extends from the two roll or woundup portions on the shafts. For identification the wound-up portions have been given the reference numeral but it is to be understood that in accordance with by invention, the diameters of wound-up portions 20 and the length of the flat portion ofthe strip l4 therebetween can be changed.

The upper heating-electrode 2 is supportedin any suitable manner so that one or both of its ends can be independently wound or unwound. either manually by turning the shaft IE or I8, or automatically in any su tabl manner. As more particularly shown in Fig. 2, a fixed main support 22 receives a plurality of screws 24 Whichare vertically adjustable in the support 22 by means of nuts 26. The lower ends of the screws 24 carry an intermediate rectangular insulating supporting frame 28 which directly carries the heating-electrode 2. Frame 28 centrally carries a plurality of insulators 30 to the far ends of which is secured a rigid member 32 in the form ofa metal plate. A central portion of the strip I4 is secured, as by welding, to the underside of the plate 32, so that this portion of the strip will also be fixed in a position determined by the adjustment of the screws 24.

Screw-rods 34 are carried at the four corners of the intermediate insulating frame 28. Each of these screw-rods 34, terminates in a ring or bearing 35 which rotatably receives an end of a shaft IE or I8 that extends longitudinally beyond the wound-up portion of the strip l4. The position of each screw-rod 34 is transversely adjustabl'e with respect to the intermediate frame 28, as for example, by having each rod ride in a slot 38 which is elongated transversely to the direction of movement of the conveyor H), as shown inFig. 5. Nuts 40 on the screw-rods 34 clamp the rods to the frame 28 in any desired adjusted position. When the nuts are loose, the screwrods34 slide in the slots 38 to allow the width of the strip Hi to be adjusted.

The distance between the heating-electrodes 2 and 4 can be adjusted through. the nuts Men the screw-rods '24,. The width of the upper heatingelectrode 2, from shaft I6 to shaft 18, can obviously be changed by winding or unwinding more or less of the strip l4 on the shaft 16, or theshaft 18, or both.

Changing the width of the heating-electrode 2' is accompanied by a change in the position of one or both of the wound-up portions 20 of the strip 14 with respect to its fixed centralportion at the plate 32. This changes'the overlap of the surface ofone heating-electrode with respect to the surface of the other; The position of each wound-up portion 20 with respect to this plate can also be changed by raising or lowering a shaft ft or H! in instances where it is desired to provide a non-uniform electric fieldalong thepath of travel of the material. However, it may be desirable' to keep the flat portion of the strip l4in a single level plane, in which case variations in the diameter of the wound portions of the strip on the shafts l6 and I8 may becompensated for by adjusting the nuts 40. In order to helpin aligning the flat portion of the strip so that it will be level whenever the strip width is adjusted, each of the bearings 36 has an insulating cord 42 secured thereto. Each cord passes around a freely rotatable pulley 44 and extends to a suspended weight 45' to which it is tied. The weights 46 tend'to keep the flat strip portiontaut, while the apparatus is being adjusted. A particular advantage of using a single piece of metal for the strip I 4 for the full width of the heating-electrode 2, resides in the fact that a smooth and continuous surface for bounding the high-frequency heating-electric field in the work-space 6 is easily and economically provided.

From the foregoing structure it is apparent that I have provided dielectric heating means consisting of two relatively insulating heatingelectrodes, one of which is wide enough to support a, conveyorand'the other of which can be adjusted to the width of the material that hape pens to be carried on the conveyor. In adjustingeither the height or width of the upper heat ing-electrode 2, the. capacitance load branch circuit, which is fed by the high-frequency power supply, is altered; and, as explained in the copencling application of W. H. Anderson and A. C. Frey, Serial No. 755,756, filed June 19', 1947, now Patent Number 2,583,133 it is sometimes desirable to have the heating'electrodes 2 and 4 in p'artof a parallel circuit which is tuned or resonant to the supply'frequency, or in part. of a scribed, this may be done automatically by means of an adjustable tuning strap 50 at one or more An adjustable corners of the heating-electrodes. rolled tuning strap and a combination therewith are shown and claimed in the aforesaid application.

Each strap 50 has an end secured to the lower heating-electrode 4. on a protruding portion of the'shaft IE or I8, as the case may be, but in a rotary direction which is opposite to that in which the strip I4 is wound on the particular shaft. In other words, looking at Fig. 2, the wound portion of the strip I4 at the left, is wound clockwise on the shaft I8, whereas the strap 50 is wound counterclockwise on the same shaft. Accordingly, when this shaft I8 is turned for making the heating-electrode 2 narrower or decreasing the capacitance between the heating-electrodes 2 and 4, a strap 50 unwinds and increases the inductance across the heating-electrodes 2 and 4 across which it is electrically and mechanically connected. The inductance strap or straps 50 need not be of uniform width but can be shaped so as to change the inductance in accordance with the variation in the capacitance between the heating-electrodes. In order to keep each strap-loop open and taut, an open slide member 52 may be provided through which the strap can slide. An insulating cord 54 is secured to the slide member 52, and is held in tension by a weight 56, so that the slide member presses on the strap-loop and tends to keep it open.

Instead of varying the inductance strap and the width of the upper heating-electrode 2 bya common mechanism, each inductance strap can be varied by looping one end of it around a shaft IE or I8, and carrying the other end on a shaft carried on the lower part of the lower heatingelectrode 4. Such an embodiment is shown in Fig. 6, in which a strap 60 has a turned end 62, having a hole through which a shaft, corresponding to I6 or I8, freely passes. The other end of the strap 60 is wrapped around a shaft in a gearing 64 driven by a reversible electric motor 66, as explained in the aforesaid patent application. -A further feature of Fig. 6 lies in the supporting of the adjustable rods, whichcorrespond to the rods 34, on rollers 68.

While I have described my invention in several preferred forms, it is obvious to one skilled in the art that the embodiments described are subject to wide variations and modifications within the principles of my invention.

I claim as my invention:

1. A dielectric heating means for heating different materials, comprising, in combination, a pair of spaced relatively insulated heating-electrodes, said heating-electrodes having substantially parallel and facing planar surfaces adapted to terminate an electric field, the said surface of a first of said heating-electrodes being smooth and unbroken throughout with an exposed area that faces the other of said heating-electrodes, said exposed area being adjustable respecting its physical dimensions, a conveyor device for carrying material in a predetermined direction between said heating-electrodes, the first said heating-electrode comprising a single and undivided member having a movable portion which is adjustable relative to the rest of the first heatingelectrode for increasing and decreasing the size of its said surface.

Its opposite end is wound 25A dielectric heating means for heating dif ferent materials, comprising, in combination, a pair'of spaced relatively insulated heating-electrodes, said heating-electrodes having substantially parallel and facing planar surfaces adapted to terminate an electric field, the said surface of a first of said heating-electrodes being smooth and continuous throughout, a conveyor device for carrying material in a predetermined direction between said heating-electrodes, the first said heating-electrode having a movable portion which is adjustable for increasing and decreasing the size of its said surface, with said movable portion comprising a flexible strip forming a part of said surface.

3. A dielectric heating means for heating different materials, comprising, in combination, a pair of spaced relatively insulated heating-electrodes, said heating-electrodes having substantially parallel and facing planar surfaces adapted to terminate an electric field, the said surface of a first of said heating-electrodes being smooth and continuous throughout, a, conveyor device for carrying material in a predetermined direction between said heating-electrodes, the first said heating-electrode having a movable portion which is adjustable for increasing and decreasing the size of its said'surface, with said movable portion comprising a flexible strip forming a part of said surface, and characterized in addition by a winding means disposed so that a portion of said flexible strip can be wound on and unwound from said winding means. i 4. A dielectric heating means for heating, comprising, in combination, a pair of spaced relatively insulated heating-electrodes, a first of said heating-electrodes comprising a predetermined fixed portion and a flexible portion having an end secured to the fixed portion, both portions defining a part of said work-space, and means for changing the expanse of said flexible portion along said part of said work-space, whereby to change the size of said work-space.

5. An invention in accordance with claim 4 but further characterized by said means for changing the expanse of said flexible portion being a winding device at the other end of said flexible portion.

6. A dielectric heating means of variable capacitance for heating different materials, comprising, in combination, a pair of relatively insulated heating-electrodes, means for supporting said heating-electrodes in predetermined spaced relation to form a work-space therebetween, a first of said heating-electrodes comprising a first fixed portion and a second flexible portion movable with respect to said first portion, said portions being on the same side of and forming part of. said work-space, and being "joined together so as to extend successively in a direction along said work-space.

'7. An invention including that of claim 6 but further characterized by adjusting means attached to said flexible portion for changing the position of an end of said flexible portion of said strip with respect to said fixed portion, said adjusting means comprising a winding member having an axis associated with an end of said flexible portion, which is away from said fixed portion, upon which said flexible portion can be wound and unwound to variable extents for altering the extent of said first heating-electrode with respect to the other of said heating-electrodes said winding member also being linearly movable in'a line substantially perpendicular to its axis.

8. An invention including that of claim 6 but further characterized by said supporting means comprising a winding member associated with an end of said flexible portion, which end is away from said first portion, for Winding and unwinding said flexible portion to variable extents, and means for keeping the unwound portion of said flexible strip taut.

9. An invention including that of claim 6 but characterized further by said portions comprising a strip having a continuous smooth surface extending across both of said portions.

10. An invention including that of claim 6 but characterized further by positioning means for changing the position of an end of said flexible portion with respect to said fixed portion and the other of said heating-electrodes, said positioning means comprising mechanism keeping said flexible portion taut.

11. An invention including that of claim 10 but characterized by said positioning means comprising a Winding means for winding and un'- winding said flexible portion to variable extents, said winding means comprising a rotatable bar with an end of said flexible portion being wrapped around said bar, and further characterized by a variable inductance strap, said strap having its ends electrically and mechanically fastened to i said heating-electrodes, the mechanical fastening including a member for increasing and decreasing the length of said strap.

12. A dielectric heating means of a type described comprising, a supporting frame, a heating-electrode, an adjustable rod-mechanism secured to the frame for adjustably carrying the heating-electrode, said heating-electrode comprising a flexible strip having a spirally wrapped portion and an unwrapped portion, means for changing the size of the surface of said heatingelectrode, said means comprising a winding and unwinding mechanism for said spirally wrapped portion, and means for keeping said unwrapped portion taut.

13. A dielectric heating-electrode of a type described comprising a plate member having a flexible strip secured to a face thereof, said strip having an end portion extending beyond said plate member, and a bar member on which said end portion is spirally wound. I

14. An invention including that of claim 13 but characterized further by said strip member substantially covering the face of the plate member.

15. Dielectric heating means comprising, a pair fi'rst'of said electrodes comprising a rollable portlon, means to wind and unwind said portion to vary said capacitance, and means operable simultaneously with said winding means to adjust said device to increase said inductance when said portion is wound and to decrease said inductance when said portion in unwound.

l7. Dielectric heating means comprising a pair of'spaced heating-electrodes havin facing overlapping surfaces, means supporting said heatingelectrodes in an arrangement in which said surfaces are spaced and have a predetermined overlap and form a capacitance therebetween, a variable inductance device connected across said heating-electrodes to form an inductance, means operable for changing said arrangement to change said overlap, thereby varying said capacitance, and means simultaneously operable with said arrangement-varying means'for varying said device to decrease its inductance when said overlap is increased and to increase its inductance when said overlap is decreased.

' 18. A dielectric heating means of variable capacitancefor heating different materials, comprising, in combination, a pair of relatively insulated heating-electrodes, means for supporting said heating-electrodes in predetermined spaced relation to form a work-space therebetween, and a conveyor device to carry work into and out of said work-space in a predetermined direction, a first of said heating-electrodes comprising an integral and undivided member, said member be ing adjustable such that it provides an exposed surface of adjustable width transversely of said direction.

19. A dielectric heating means as defined in claim 18 but further characterized by said surface being smooth and unbroken over its entire exposed surface in all of its adjustments.

20. A dielectric heating means as defined in claim 18 but further characterized by an adjustable inductance device connected across said heating-electrodes, and means for simultaneously adjusting the width of said surface and said device but in opposite magnitude-directions.

RICHARD H. HAGOPIAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

